1. Field of the Invention
This invention relates to a dielectric detecting system of a control device for controling a device such as an automatic fastening seat belt, a power operated window and an automatic locking device of a door, comprising a pair of electrodes which sense the variation of an electrostatic capacitance between the electrodes and used for detecting the presence of a passenger in a vehicle.
2. Description of the Related Art
A conventional dielectric detecting system is disclosed in Japanese Patent publication No. 62-91882. The dielectric detecting system disclosed in the prior art comprises a conductive plate disposed in a seat of a vehicle as a sensor electrode and a vehicle body as an earth electrode, and detects the presence of a passenger as a dielectric to be detected by means of sensing the variation of an electrostatic capacitance between the electrodes.
However the system sometimes detects a dielectric which should not be detected such as a seat cushioning pad by the transition of the environments (such as the transformation of the shape of the seat cushioning pad).